The objective of this research is to investigate the effects of halothane, one of the most commonly employed inhalational anesthetics, on the ulstrastructure of neurally-derived cells. In these studies, particular emphasis is being placed on the effects of haolthane on microtubules and microfilaments and the role of these fibrous organelles in cell differentiation and division as well as axonal transport. We have shown that concentrations as low as 0.3-0.6% halothane lead to the disassembly of actin-like microfilaments measuring 40-80A in diameter. These results have been confirmed in experiments using heavy-meromyosin (HMM) isolated from rabbit skeletal muscle myosin. We have also demonstrated actin-like microfilaments in the mitotic apparatus of these cells which are structurally labile in the presence of halothane concentrations having little effect on spindle microtubules. These experiments will be broadened to include a number of cell types and volatile anesthetic agents as will experiments investigating possible distributional changes in specific enzymes in the presence of halothane. Continuing experiments are planned to further characterize the mechanism whereby halothane induces macrotubular changes in microtubular structure in crayfish axons and determine the composition and function of microtubule-associated filamentous complexes.